Arc igniting device



July 28, 1942. P. L. SPENCER 2,290,997

v ARC IGNITING DEVICE Filed Nov. 13, 1939 3 Sheets-Sheet l e n 9 G 9 9 l f 994v9 1v n T. J d \d7 P v A l my i n.

INVENToR .R. E E Y P 5 L u P. L. SPENCER 4ARCl IGNITING DEVICE Filed Nov. 13, 1939 July 28, 1942.

5 Sheets-Sheet 2 lNvEN-roa PancY L PENcxaw,y BY vlv -r-rY.

July 22,1942. P. L, SPENCER 2,290,827

RC IGNITING DEVICE Filed No?. 13, 19.39 3 Sheets-Sheet 3 Patented July 28, 1942 ARC IGNITING DEVICE.

Percy L. Spencer, West Newton, Mass., assig'nor to Raytheon Manufacturing Company, Newton, Mass., a corporation 'of Delaware Application November 13, 1939, Serial No. 303,963

(Cl. Z50-27.5)

13 Claims.

This invention relates to arc discharge devices of the type in which an igniting electrode arrangement is provided for the starting of an arc spot on a pool type cathode. The igniting electrode is of the type which is separated by an insulating wall from the cathode, and initiates an arc by means of a high voltage impressed between the cathode and the igniting electrode.

An object of this invention is to devise an arrangement in which contamination and desensitizing of the insulating wall on the igniting electrode is prevented, and long life of the device is secured.

Another object is to increase the sensitiveness of the igniting electrode arrangement.

A further object is to provide a novel supporting structure for the igniting electrode arrangement.

The foregoing and other objects of this invention will be best understood from the following description of an exemplication thereof, reference being had to the accompanying drawings, wherein:

Fig. 1 isa vertical cross-section taken along line I-I of Fig. 3 of a tube embodying my invention, together with a diagrammatic representation of a circuit with which said tube may be used;

Fig. 2 is another vertical cross-section of the tube taken along line 2-2 of Fig. 3;

" Fig. 3 is a horizontal cross-section of the tube taken along line 3-3 of Fig. 1;

Fig. 4 is an enlarged cross-section of one of the igniting elements of the igniting electrode arrangement;

Fig. 5 is a greatly enlarged cross-section taken across one of the igniting elements;

Fig. 6 is a fragmentary cross-section taken along line 6--6 of Fig. 7 through a tube having a modified form of shield; and

Fig. 7 is a cross-section taken along line '1 -1 of Fig. 6.

horizontal portion of the conductor 5 is the igniting portion, and is covered with a layer of insulating material 6 which preferably is glass sealed to the surface of the conductor 5. This .layer is preferably as described and claimedin my co-pending application, Serial No. 251,069,

'led January 16, 1939, wherein the insulating layer is described as having a thickness of the of the vertical leg of the conductor 5 is left uncoated so that electrical connection may be made thereto. To this uncoated portion is mechanically and electrically connected an arm 8 of the supporting yoke 9. The two ends of the horizontal leg of the conductor 5 are provided with enlarged glass beads I0 and II. These enlarged .glass beads serve as oats which make the igniting element float considerably higher on the surface of the mercury pool 2 than if such enlarged glass beads werenot provided. As a result of this action, the igniter element floats at about the level as indicated in Fig. 5. Disposing the ignit- The tube as illustrated in Figs. 1 to 5, inclusive,

consists of a glass envelope I containing a. cathode 2 of the pool type. The material of this cathode preferably consists of mercury. Adaptf ed to cooperate with said cathode is an anode 3.

In order to initiate arc spots on the surface oi the pool cathode, there is provided a pair of igniting elements 4. The detailed construction of each of these igniting elements is shown most clearly in Figs. 4 and 5. Each of these igniting elementsv consists of an elongated L-shaped conductor 5 which in a particular instance may have a diameter of the order of .025 of an inch. The '5 ing element in this way substantially eliminates any danger of said element being entirely immersed in the mercury, and also appears to give increased sensitivity of starting.

As indicated in Figs. 1-3, the supporting yoke 9 is provided with a center loop I2 which surrounds a guiding sleeve I3. This guiding sleeve I3 is likewise constructed of a suitable insulating material, such as glass, and is supported from the lower wall of the envelope I by -being fused thereto, as indicated in Fig. 1. In order to support the igniting, elements 4 and to provide an electrical lead-in therefor, a lead-in rod I4 is sealed through the lower glass wall of the er.- velope I, and is insulatingly separated from the pool 2 by the glass of the seal and by the glass sleeve I3. To the upper end of the rod I4 is connected a clip I5 having a light spring I6 fastened at its upper end thereto. The lower end of said spring I 6 is secured to the yoke 9, thus providing an electrical connection to the igniting elements 4. The spring I6 may be arranged so as to exert a slight tension on the yoke 9, and in this way assist in supporting the end of the igniting structure which has the greater amount of weight. However, the major portion of the weight of the igniting structure is supported by being iioated on the surface of the mercury pool. The spring, however, does assist in maintaining the proper level of floating.

A guide rod I1 is also connected to the outer end of the clip I5. The lower endof this guide rod is insulated by having a layer of glass coated thereon, the upper end of this layer of glass being provided with an enlarged glass bead 9 which serves as a stop. The yoke 9 also carries a loop which fits loosely around the insulating coating I8 and permits the yoke to slide up and down along the rod I1. However, due to the stop bead I9, the yoke cannot move up beyond the point established thereby, and in this way it is prevented from falling off the upper end of the glass sleeve I3 even if the tube is completely inverted. The guiding action of the loops I2 and 20 also keeps the igniting structure from twisting, and thus prevents the igniting elements 4 from coming violently into contact with the surrounding tube structure, and in this way prevents damage to said elements.

Before mercury is inserted into the envelope I during the process of manufacture, the igniting elements cannot drop below a predetermined level since the top of the dam 22 forms a lower stop against which the yoke 9 comes into contact.

The electrostatic type of igniter as utilized with a pool type cathode has had the disadvantage of becoming desensitized during operation, thus unduly shortening the life of tubes utilizing such an arrangement. In accordance with my present understanding of this arrangement, such loss of sensitiveness seems to be due to contamination of the surface of the insulating member. Some of this contamination may be due to sputtered particles liberated from the anode during the running of the discharge, depositing upon the insulating surface of the igniting element. Whatever the cause may be, I have found that the life of tubes of this kind can be greatly increased by inter-posing a shield between the anode and the insulating surfaces of the igniting element. In the present arrangement I have illustrated such a shield at 2l made of electrically-conductive material and electrically connected to and supported by the upper end ofthe lead-in rod I4. As indicated by the dotted lines fromthe edges of the anode 3 in Figs. 1 and 2, the dimensions of the shield 2I are so chosen that said shield interrupts all straight-line paths from the anode to both of the igniting elements 4 4. Since sputtered particles usually travel in straight lines, all such particles are interrupted before reaching the insulating surface of said igniting elements. I believe also that when particles are sputtered, they travel at high speeds, and if they were permitted to hit the insulating, surface of the igniting elements 4 4, they would be driven into these surfaces, thus tending to accelerate the desensitization thereof. The shield ZI, as described above, eliminates such an action.

Another source of contamination of the insulating surfaces of the igniting elements is the surface of the mercury pool 2, which during operation acquires a considerable amount of impurities floating on its surface. In previous tubes, such impurities have been permitted to come into contact with the igniting element surfaces,

which contact has resulted in contamination and desensitization of the surfaces. In accordance with my present invention, this type of contamination is prevented by a dam 22 which is disposed around the igniting elements 4 4, projecting through the surface of the mercury pool 2 and spaced from the walls of the tube. The dam 22 may conveniently be formed of glass. The dam is supported with its lower edge spaced from the bottom wall by means of a plurality of glass support legs 23 disposed at spaced points around the bottom of said dam.

During operation of the device the arc spots which are established on the surface of the merculry pool will occur within the area enclosed by the dam 22. These arc spots cause relatively violent agitation of the mercury surface. This agitation, together with the action of the arc itself, expel particles from the mercury surface. These particles fly out and collide with the walls of the tube. The mercury vapor which condenses on these walls washes such particles back to the mercury pool. However, any such particles washed back in this way are returned to that portion of the pool outside of the darn 22. The impurities with which we are concerned are those which oat on the surface of the mercury because it is only these impurities which can come into contact with the igniting elements. The arc seems to exert a scouring action which in a very short length of time entirely clears the area within the dam 22 of all impurities which may be floating on said surface. These vfloating particles when returned to the region outside of the dam 22 cannot get back to the region inside said dam. However, the mercury itself can flow around the lower edges of the dam, and thus maintain the level of the pool within the dam 22 at its proper height. The arrangement as shown in Figs. 1 and 2 has the shield 2| restricted in size sufficiently to permit the free escape of such particles as are thrown out by the arc. Therefore, the arrangement accomplishes a complete shielding of the igniting elements 4 4 from sputteredfparticles liberated at the anode while permitting free escape of contaminating particles from the surface of the pool upon which the igniting elements oat,

External electrical connection may be made to the cathode by providing a cathode lead-in conductor 24 sealed through the bottom portion of the envelope I, while external electrical connection may be made to the anode 3 by providing a lead-in conductor 25 sealed through the upper end of said envelope.

The tube as illustrated `may be operated in any'suitable circuit. In Fig. l I have illustrated diagrammatically a typical circuit in which said tube may be used. In order to supply the tube with power, an input transformer 26 is provided having a primary winding 21 adapted to be 'connected to a suitable source of alternating current, and a secondary winding 28. One end of the secondary winding 28 is connected to the leadin conductor 25, while the other end of said secondary winding is connected through a load 29 to the lead-in conductor 24, and thus to the cathode 2. In order to initiate an arc spot on the pool cathode 2, each time the anode 3 becomes positive, an igniting voltage is connected between the lead-in rod I4 and the lead-in conductor 24. These igniting voltage impulses may be supplied from a pair of leads 3I connected to a suitable source of alternating current and tting intoan igniting voltage control 30. This voltage controlmay be of any suitable type, for example of the rkind as described and claimed in the copending application of John W. Dawson, Serial No.l 284,502, which supplies substantially solely positive voltage peaks to the igniting structure. These positive voltage peaks occur during the time that the anode 3 is positive with respect to the anode 2. When such voltage peaks occur, an arc spot is initiated on the surface of the mercury pool, and current flows between the cathode and anode.

I have found also that the presence of the shield 2l .tends to prevent iiashbacks between the cathode and the anode. In order to take full advantage of this effect, the arrangement, as illustrated in Figs. 6 and 7, may be utilized. In this embodiment the shield 2l is replaced by an extended shielding member 32 of conducting material which extends across substantially the entire cross-sectional area of the envelope l between the cathode and the anode. This shielding likewise is electrically connected to and suping element, intercepting vsubstantially all straight-line paths between said anodeand the piace where said contact between said cathode and said insulating wall occurs.

4. An arc discharge device comprising an anode, a pool type cathode, anigniting element comprising a conductor insulated from said cathode by an insulating wall on said conductor, said insulating wall being in contact with the surported by the upper end of the lead-in rod I4.

In order to allow the discharge to pass between the cathode and the anode, a plurality of openings 33 are provided in said shield. I have found that in this arrangement the discharge, which is initiated by the igniting voltage impulses supplied to the igniting structure, passes readily through the openings 33 to the anode.

Of course it is to be understood that -this invention is not limited to the particular arrangement as described above as many equivalents will suggest themselves to those skilled in the art. For example, other types of arc cathodes could be utilized, and other types and numbers of anodes could be provided. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. An arc discharge device comprising an anode, a pool type cathode, an igniting element comprising a conductor insulated from said cathode by an insulating wall on said conductor. said insulating wall being in contact with the surface of said cathode, and a shield interposed between said anode and said igniting element and electrically connected to said igniting element, intercepting substantially all straight-line paths between said anode and the place where said contact between said cathode and said insulating wall occurs.

2. An arc discharge device comprising an envelope containing an anode, a p ool type cathode, an igniting element in contact with the surface of said cathode, a dam projecting through the surface of said cathode and separating the place where said contact between said cathode and said'igniting element occurs from the region adjacent the interior walls of said envelope, and a shield interposed between said anode and said igniting element and electrically connected to said igniting element, intercepting substantially all straight-line paths between said anode and the place where said contact between said cathode and said igniting element occurs.

3. An arc discharge device comprising an envelope containing an anode, a pool type cathode, an igniting element comprising a conductor in. sulated from said cathode by an insulating wall on said conductor, said insulating wall being in contact with the 'surface of said cathode, a dam projecting through the surface of said cathode and separating the place where said contact between said cathode and said insulating wall occurs from the region adjacent the interior walls of said envelope, and a shield interposed between said anode and said igniting element and electrically connected to said lgnitface of said cathode, and electrically-conductive means electrically connected to said igniting element and interposed between said anode and the region where said contact occurs between said cathode and said insulating wall for shielding said region from material sputtered from said anode. l

5. An arc discharge device comprising an anode, a pool type cathode, an igniting element in contact withV the4 surface of said cathode, means for gathering impurities in said tube in a restricted portion thereof and for keeping said impurities from reaching the region where said contact between said cathode and said igniting element occurs, and electrically-conductive means electrically connected to said igniting element and interposed between said anode and said region for shielding said region from materialsputtered from' said anode.

6. An arc discharge device comprising an anode, a pool type cathode, an igniting element comprising a conductor insulated from said cathode by an insulating Wall on said conductor, said insulating wall being in contact with the surface of said cathode, means for gathering impurities in said tube in a restricted portion thereof and for keeping said impurities from reaching the region where said contact between said cathode and said 'insulating wall occurs, and electrically-conductive means electrically connected to said igniting element and interposed between said anode andsaid region for shielding said region from material sputtered from said anode.

7. An arc discharge device comprising an anode, a pool type cathode, an'igniting element comprising a conductor insulated from said cathode by an insulating wall on said conductor, said insulating wall being in contact with the surface of said cathode, and a shield interposed between said anode and said igniting element, intercepti ing substantially all straight-line paths between said anode and the place where said contact between said cathode and said insulating wall occurs, said shield being electrically connected to said conductor and extending substantially across the entire cross-section of the discharge path between said cathode and anode, said shield being perforated in order to permit a discharge to pass between said cathode and anode.

8. An arc discharge device comprising an anode, a pool type cathode, anigniting element comprising a conductor insulated from said cathode by an insulating wall on said conductor, said insulating wall being in contact with the surface of said cathode, said igniting elementV being iioated on the surface of said pool and provided with float means to cause said igniting element to iioat at a higher level than in absence of said float means.

9. An arc discharge device comprising an envelope containing an anode, a pool type cathode,

an igniting element in contact with the surface of said cathode, said igniting element being oated on the surface of said pool, and relatively stationary supporting' means for said igniting element, allowing a limited vertical motion of said igniting element.

l0. An arc discharge device comprising an envelope containing an anode, a pool type cathode, an igniting element in contact with the surface of said cathode, said igniting element being oated on the surface of said pool. relatively stationary supporting means for said igniting element, allowing a limited vertical motion of said igniting element, and stop means on said supporting means for limiting saidmotion when said igniting element is displaced to a considerable degree in either direction beyond its normal floating position.

1l. An arc discharge device comprising an envelope containing an anode, a pool type cathode, an igniting element in contact with the surface of said cathode, said igniting element being floated on the surface of said pool, relatively stationary supporting means for said igniting element, allowing a limited vertical motion ofsaid igniting element, stop means on said supporting means for limiting said motion when said igniting element is displaced to a considerable degree in veither direction beyond its normal floating position, and means for constraining horizontal motion of said igniting element to substantially its normal floating position.

12. An arc discharge device comprising an anode, a pool type cathode, an igniting element comprising a conductor insulated from said cathode by an insulating wall on said conductor, said insulating wall being in contact with the surface of said cathode, said insulating wall being locally increased in size to provide oat means to cause said igniting element to float at a higher level than in absence of said float means.

13. An arc discharge device comprising an anode, a pool type cathode, an igniting element comprising an elongated conductor insulated from said cathode by an insulating wall on said conductor, said insulating wall being in contact with the surface of said cathode, saidy insulating wall being increased in size at the end of said elongated conductor to provide float means to cause said igniting element to float at a higher level than in absence of said float means.

PERCY L. SPENCER. 

